Safety risk is expressed in terms of probability and severity. Currently, Military Standard (MIL-STD)-882D provides a matrix whereby, given a probability and severity, the risk level can be determined. Currently, when risk is quantified in terms of probability and severity, the worst credible scenario is typically used as the single risk scenario. While that approach increases the confidence that the assessed risk represents the worst possible outcome, it may not provide a comprehensive picture of all relevant risk (e.g., such as the case where there is a credible catastrophic scenario with a very small likelihood of occurrence, but also a serious scenario with a relatively high likelihood of occurrence). This paper proposes an approach where a broad picture of risk may be obtained by expressing risk of a mishap as a series of scenarios and then using a summing technique to obtain a Composite Risk Index (CRI). The approach utilizes factors representing the big picture of risk, such as severities of possible mishap effects and population size (affecting composite probability). The purpose of this approach is not to establish an absolute measure for risk, but to provide a balanced expression of risk level to support sound safety risk decisions.
展开▼
